Ink jet printing is a well-known printing technique by deposition of an ink composition from a reservoir onto a substrate. The deposition is conventionally accomplished by spraying droplets of the ink composition from the reservoir, without having the reservoir touch the substrate. By controlling the location of deposit of the droplets, images or printed characters are formed on a surface of the substrate.
Ink compositions typically contain an aqueous carrier medium and a colorant. The colorant may be a pigment, a dye or a mixture thereof. The colorant imparts color to the ink composition, and in turn, to the substrate after printing. As used herein, "pigment" refers to a colorant that does not dissolve in the ink composition. As used herein, "dye" refers to a colorant that dissolves in the ink composition.
Wismer et al., U.S. Pat. No. 4,007,141, disclose opaque films comprising a film-forming binder material and discrete particles which contain cells or voids. Wismer et al. teach that the opaque films may optionally contain dyes or pigments, and that the discrete particles act as an opacifying agent.
Loria et al., U.S. Pat. No. 4,880,465, disclose an ink composition having dye compounds and no pigment. Loria et al. teach that the ink composition contains opacifying agents, such as hollow microspheres filled with water, a resin component and a carrier. Loria et al. further teach that the ink composition dries after printing, wherein the water within the hollow microspheres evaporates to form an ink coating with air filled microvoids. The air filled microvoids scatter light, causing an opaque image to be produced.
Fasano, U.S. Pat. No. 5,135,568, discloses a method for improving the fluorescence of a coating by adding hollow polymer particles which scatter ultraviolet light and shorter wavelength visible light.
Mead et al., U.S. Pat. No. 5,596,027, disclose an ink composition for printing on substrates comprising a carrier, a colorant, a polyamine and an acidic resin. Mead et al. teach that the colorant may be selected from the group consisting of dyes, pigments, hollow microspheres and combinations thereof. Mead et al. further teach that the hollow microspheres are opacifying agents, and that the polyamine interacts with the acidic resin to provide a smear resistant and durable printed image.
Alexiou, U.S. Pat. Nos. 5,594,045 and 5,726,221, discloses correction fluid comprising a particulate opacifier, a water-soluble or water-dispersible binder, water, a di- or tri- or quaternary ammonium compound, and, optionally, hollow microspheres of hydrated alumina, alumina-silica alloy, or acrylate-styrene copolymer.
Substrates printed with ink compositions may smear when wetted and rubbed. Unfortunately, many prior art compositions require significant amounts of resins or polyamine compounds to achieve acceptable wet rub resistance, and these ingredients may interfere with other ingredients and adversely affect desired ink properties.
Accordingly, a need exists to minimize such smearing by improving properties of the ink composition such as wet rub resistance, without sacrificing other desired properties of the ink composition such as stability, maintainability, print quality, waterfastness and lightfastness. A need also exists to provide ink compositions having an optimal color gamut when used in combination with other ink compositions.